Telstar, when we're operating at minimum final approach spacing we have an 880yd buffer between perfection and setting the snitch off with the associated possible suspension whilst it's investigated (think guilty until proven innocent).
That's not a lot in time or distance at the speeds being flown and whilst I in no way excuse the STN bloke for having a go at you on the r/t it is one reason why we can get a little touchy about how accurately final approach speeds are, or are not, being flown.